arXiv subjects

Y. Q. Fang

Publications and source records attributed to Y. Q. Fang.

280 records · Page 16Linked to original sources

arXiv2023

Measurement of the cross sections for $e^+e^-\toηπ^+π^-$ at center-of-mass energies between 2.00 and 3.08 GeV

Using data samples collected at center-of-mass energies between 2.000 and 3.080 GeV with the BESIII detector operating at the BEPCII collider, a partial-wave analysis is performed on the process $e^+e^-\toηπ^+π^-$. In addition to the dominant $e^+e^-\toρη$ component, the $e^+e^-\to a_2(1320)π$ process is also sizeable, contributing up to 24% of the total reaction. The measured cross sections of the process $e^+e^-\toηπ^+π^-$ are systematically higher than those of BaBar by more than $3σ$ at center-of-mass energies between 2.000 and 2.300 GeV. In the cross section lineshape for $e^+e^-\to a_2(1320)π$, a resonant structure is observed with a significance of $5.5σ$, with $M=(2044\pm31\pm4)$ MeV/$c^2$, $Γ=(163\pm69\pm24)$ MeV and $\mathcal{B_{R}}\cdotΓ_{e^+e^-}^{R}=(34.6\pm17.1\pm6.0)$ eV or $(137.1\pm73.3\pm2.1)$ eV. In the cross section lineshape for $e^+e^-\toρη$, an evidence of a dip structure around 2180 MeV/$c^2$ is observed with statistical significance of $3.0σ$.

hep-ex↗

arXiv2023

Improved measurement of the decays $η' \to π^{+}π^{-}π^{+(0)}π^{-(0)}$ and search for the rare decay $η' \to 4π^{0}$

Using a sample of 10 billion $J/ψ$ events collected with the BESIII detector, the decays $η' \to π^{+}π^{-}π^{+}π^{-}$, $η' \to π^{+}π^{-}π^{0}π^{0}$ and $η' \to 4 π^{0}$ are studied via the process $J/ψ\toγη'$. The branching fractions of $η' \to π^{+}π^{-}π^{+}π^{-}$ and $η' \to π^{+}π^{-}π^{0}$ $π^{0}$ are measured to be $( 8.56 \pm 0.25({\rm stat.}) \pm 0.23({\rm syst.}) ) \times {10^{ - 5}}$ and $(2.12 \pm 0.12({\rm stat.}) \pm 0.10({\rm syst.})) \times {10^{ - 4}}$, respectively, which are consistent with previous measurements but with improved precision. No significant $η' \to 4 π^{0}$ signal is observed, and the upper limit on the branching fraction of this decay is determined to be less than $1.24 \times {10^{-5}}$ at the $90\%$ confidence level. In addition, an amplitude analysis of $η' \to π^{+}π^{-}π^{+}π^{-}$ is performed to extract the doubly virtual isovector form factor $α$ for the first time. The measured value of $α=1.22 \pm 0.33({\rm stat.}) \pm 0.04({\rm syst.})$, is in agreement with the prediction of the VMD model.

hep-ex↗

arXiv2023

Study of the decay $J/ψ\to ϕπ^{0}η$

Based on $(10.09 \pm 0.04) \times 10^9$ $J/ψ$ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay $J/ψ\to ϕπ^{0}η$ is performed. We observe for the first time two new structures on the $ϕη$ invariant mass distribution, with statistical significances of $24.0σ$ and $16.9σ$; the first with $J^{\rm PC}$ = $1^{+-}$, mass M = (1911 $\pm$ 6 (stat.) $\pm$ 14 (sys.))~MeV/$c^{2}$, and width $Γ= $ (149 $\pm$ 12 (stat.) $\pm$ 23 (sys.))~MeV, the second with $J^{\rm PC}$ = $1^{--}$, mass M = (1996 $\pm$ 11 (stat.) $\pm$ 30 (sys.))~MeV/$c^{2}$, and width $Γ$ = (148 $\pm$ 16 (stat.) $\pm$ 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the $f_0(980)-a_0(980)^0$ mixing signal in $J/ψ\to ϕf_0(980) \to ϕa_0(980)^0$ and the corresponding electromagnetic decay $J/ψ\to ϕa_0(980)^0$ are measured with improved precision, providing crucial information to understand the nature of $a_0(980)^0$ and $f_0(980)$.

hep-ex↗

arXiv2023

Study of the doubly Cabibbo-suppressed decays $D^+_s\to K^+K^+π^-$ and $D^+_s\to K^+K^+π^-π^0$

Based on 7.33 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, the experimental studies of the doubly Cabibbo-suppressed decays $D^+_s\to K^+K^+π^-$ and $D^+_s\to K^+K^+π^-π^0$ are reported. We determine the absolute branching fraction of $D^+_s\to K^+K^+π^-$ to be (${1.23^{+0.28}_{-0.25}}({\rm stat})\pm0.06({\rm syst})$) $\times 10^{-4}$. No significant signal of $D^+_s\to K^+K^+π^-π^0$ is observed and the upper limit on its decay branching fraction at 90\% confidence level is set to be $1.7\times10^{-4}$.

hep-ex↗

arXiv2023

Measurement of $e^{+}e^{-}\rightarrowηJ/ψ$ Cross Section from $\sqrt{s}=$ 3.808 GeV to 4.951 GeV

Using data samples with an integrated luminosity of 22.42 fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the $e^{+}e^{-}\rightarrow\etaJ/ψ$ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with $ψ(4040)$, two additional resonances, and a non-resonant component is performed. The mass and width of the first additional state are $(4219.7\pm2.5\pm4.5) \rm{MeV}/\rm{c}^2$ and $(80.7\pm4.4\pm1.4) \rm{MeV}$, respectively, consistent with the $ψ(4230)$. For the second state, the mass and width are $(4386\pm13\pm17) \rm{MeV}/\rm{c}^2$ and $(177\pm32\pm13) \rm{MeV}$, respectively, consistent with the $ψ(4360)$. The first uncertainties are statistical and the second ones are systematic. The statistical significance of $ψ(4040)$ is $8.0σ$ and those for $ψ(4230)$ and $ψ(4360)$ are more than $10.0σ$.

hep-ex↗

arXiv2023

First measurement of $ΛN$ inelastic scattering with $Λ$ from $e^{+} e^{-} \rightarrow J/ψ\to Λ\barΛ$

Using an $e^+ e^-$ collision data sample of $(10087 \pm 44)\times10^6 ~J/ψ$ events taken at the center-of-mass energy of $3.097~\rm{GeV}$ by the BESIII detector at the BEPCII collider, the process $Λ+N \rightarrow Σ^+ + X$ is studied for the first time employing a novel method. The $Σ^{+}$ hyperons are produced by the collisions of $Λ$ hyperons from $J/ψ$ decays with nuclei in the material of the BESIII detector. The total cross section of $Λ+ ^{9}{\rm Be} \rightarrow Σ^+ + X$ is measured to be $σ= (37.3 \pm 4.7 \pm 3.5)~{\rm mb}$ at $Λ$ beam momenta within $[1.057, 1.091]~{\rm GeV}/c$, where the uncertainties are statistical and systematic, respectively. This analysis is the first study of $Λ$-nucleon interactions at an $e^+ e^-$ collider, providing information and constraints relevant for the strong-interaction potential, the origin of color confinement, the unified model for baryon-baryon interactions, and the internal structure of neutron stars.

nucl-ex↗

arXiv2021

Observation of Topological Superconductivity in a Stoichiometric Transition Metal Dichalcogenide 2M-WS2

Topological superconductors (TSCs) are unconventional superconductors with bulk superconducting gap and in-gap Majorana states on the boundary that may be used as topological qubits for quantum computation. Despite their importance in both fundamental research and applications, natural TSCs are very rare. Here, combining state of the art synchrotron and laser-based angle-resolved photoemission spectroscopy, we investigated a stoichiometric transition metal dichalcogenide (TMD), 2M-WS2 with a superconducting transition temperature of 8.8 K (the highest among all TMDs in the natural form up to date) and observed distinctive topological surface states (TSSs). Furthermore, in the superconducting state, we found that the TSSs acquired a nodeless superconducting gap with similar magnitude as that of the bulk states. These discoveries not only evidence 2M-WS2 as an intrinsic TSC without the need of sensitive composition tuning or sophisticated heterostructures fabrication, but also provide an ideal platform for device applications thanks to its van der Waals layered structure.

cond-mat.mtrl-sci↗

arXiv2018

Superconductivity in the metastable 1T' and 1T''' phases of MoS$_2$ crystals

Transition-metal dichalcogenides open novel opportunities for the exploration of exciting new physics and devices. As a representative system, 2H-MoS$_2$ has been extensively investigated owing to its unique band structure with a large band gap, degenerate valleys and non-zero Berry curvature. However, experimental studies of metastable 1T polytypes have been a challenge for a long time, and electronic properties are obscure due to the inaccessibility of single phase without the coexistence of 1T', 1T'' and 1T''' lattice structures, which hinder the broad applications of MoS$_2$ in future nanodevices and optoelectronic devices. Using ${K_x(H_2O)_yMoS_2}$ as the precursor, we have successfully obtained high-quality layered crystals of the metastable 1T'''-MoS$_2$ with $\sqrt{3}a\times\sqrt{3}a$ superstructure and metastable 1T'-MoS$_2$ with a$\times$2a superstructure, as evidenced by structural characterizations through scanning tunneling microscopy, Raman spectroscopy and X-ray diffraction. It is found that the metastable 1T'-MoS$_2$ is a superconductor with onset transition temperature (${T_c}$) of 4.2 K, while the metastable 1 T'''-MoS$_2$ shows either superconductivity with Tc of 5.3 K or insulating behavior, which strongly depends on the synthesis procedure. Both of the metastable polytypes of MoS$_2$ crystals can be transformed to the stable 2H phase with mild annealing at about 70 $^{\circ}$C in He atmosphere. These findings provide pivotal information on the atomic configurations and physical properties of 1T polytypes of MoS$_2$.

cond-mat.supr-con↗

arXiv2004

The Higgs Working Group: Summary Report 2003

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

hep-ph↗

arXiv2004

Prospects for Higgs Searches via VBF at the LHC with the ATLAS Detector

We report on the potential for the discovery of a Standard Model Higgs boson with the vector boson fusion mechanism in the mass range $115<M_H<500 \gev$ with the ATLAS experiment at the LHC. Feasibility studies at hadron level followed by a fast detector simulation have been performed for $H\to W^{(*)}W^{(*)}\to l^+l^-\sla{p_T}$, $H\toγγ$ and $H\to ZZ\to l^+l^-q\bar{q}$. The results obtained show a large discovery potential in the range $115<M_H<300 \gev$. Results obtained with multivariate techniques are reported for a number of channels.

hep-ph↗